In semiconductor manufacture, a single semiconductor die (or chip) can be packaged within a sealed package. The package protects the die from damage and from contaminants in the surrounding environment. In addition, the package provides a substantial lead system for electrically connecting the integrated circuits on the die to the outside world.
One type of semiconductor package 10 is illustrated in FIG. 1A. The package 10 includes a substrate 12 having a planar die attach surface or die site 22. A semiconductor die 16 is mounted to an upper surface of the substrate 12 on the die site 22. The die 16 is typically adhesively bonded to the substrate 12 with an adhesive layer 34. An encapsulating resin 38 encapsulates the die 16.
In addition to the die site 22 on the upper surface, the substrate 12 includes an opposing conductor surface 24 wherein conductors 18 are formed in a required pattern. A wire bond opening 26 in the substrate 12 provides access for bonding wires 28. The bonding wires 28 are connected to the conductors 18 and to bond pads (not shown) on the die 16. A glob top 40 is formed over the wires 28 for protection.
The semiconductor package 10 also includes an array of solder balls 14. The solder balls 14 are bonded to ball bonding pads 24 on the conductors 18.
As shown in FIG. 1B, the substrate 12 is initially a segment 32 of a support element 30. The support element 30 includes multiple substrates 12 (and thus multiple die sites 22). The support element is used to fabricate multiple semiconductor packages 10. The support element facilitates the fabrication process in that different operations, such as die attach and wire bonding, can be performed at the same time on each of the substrates. Following the fabrication of the semiconductor packages 10 from the support element 30, the support element is singulated into individual semiconductor packages.
The process for packaging semiconductor dice includes matching a die to each die site on the support element. The die is attached to the die site over the wire bond opening 26 so that the die may be electrically connected to the substrate. Currently available support elements typically include one or more substrates that are defective or non-functional, i.e., the substrates include “reject die sites.” Individual substrates of a support element may be non-functional for a variety of reasons, such as faulty electrical circuitry of a substrate. Such defect substrates of the support element cannot be utilized to fabricate a functional semiconductor package but cannot be separated from the support element prior to processing of the other substrates on the support element. If the defective substrates are separated from the support element, such action necessarily limits the number of substrates that may be processed at one time using the separated support element. Thus, physical separation of defect substrates from the support element prior to fabrication of the semiconductor packages is not preferred.
When functional dice are attached to the “reject die sites” of the support element and further are processed, the resulting semiconductor packages are necessarily defective. This sacrifices functional dice, thereby increasing semiconductor package manufacturing costs and decreasing yields. To avoid the added cost (i.e., sacrificing functional dice), a “reject die site” on a support element could simply be skipped or omitted during the die attach process. Regrettably, omitting attachment of a die to a die site on a support element causes problems during the encapsulation process.
During the encapsulation process, liquid encapsulation material flows over and around the attached dice and substrates of the support element. If one or more bonding slots are left open, i.e., a die is not attached to a die site of the support element, the encapsulation material flows through the uncovered opening 26. When the encapsulation material flows through such openings, it contaminates dice adjacent and/or near the uncovered opening. This is known as “bleeding or flashing.” The bleeding of encapsulation material produces even more defective semiconductor packages, further increasing manufacturing costs and lowering yield. Moreover, bleeding of the encapsulation material may stick to the mold body and contaminate the next support element processed through the encapsulation machine.
In attempt to avoid (1) sacrificing functional dice by attaching the dice on reject die sites, (2) contaminating adjacent dice and mold bodies by omitting attachment of dice to reject die sites, and (3) processing support elements that include a minimal number of substrates due to prior separation of the defective substrates, the industry pays a premium price for support elements having no reject die sites. This also increases semiconductor package manufacturing costs.
Accordingly, there is a need for a process for making semiconductor packages using support elements having one or more reject die sites without contaminating adjacent dice and without destroying functional dice by attaching the dice to reject die sites. To this end, there is a need for support elements having modified reject die sites to eliminate risk of contamination of adjacent dice on a support element, during encapsulation and to preserve functional dice for use on functional die sites.